Condenser



March l5, "1932. K. M. McLAuGHLaN v 12,849,499

' coNDENsER I I 'Filed sept. 29. 1930 lli il in e vQ um un *i LE'LLEQ@.aw meelilnmuiuwi Patented Mar. 1s, 1932 i "UNIT-ED STATES'.

PATENT o1-FICE KENNETH I. KCLAUGHLIN, OF PHILADELPHIA, PENNSYLVANIA,ASSIGNOR T A'I'wnrnn KENT MANUFACTURING .a conrolwrroN or PENNSYLVANIAOOMPAN Y, PHILADELPHIA, PENNSYLVANIA,

CONDENSER Application led September 29, 1930. Serial No. 484,988.

g radio-frequency circuits of radio receiving apparatus.

Particularly in compact radio receivers in which the lloud-speaker -islocated near other components of the receiving apparatus',

5 sound disturbances often result which are generically termedmicrophonic noises. I have found that the plates of the tuningcondensers may be set into vibration, as by the sound vibrations of theloud speaker, result- 1-5 ing in variation of the resonant frequency ofthe receiver and modulation of mcoming radio-frequency energy at audiofrequency corresponding to the period of the vibrating lates. After theradio-frequency is rectied by the' detector of the receiver, thevibration of the rotor plates is reproduced in the loud speaker as soundvibrations which impings upon and maintain the plates in vibration, thenoise building up in amplitude by what may be termed sound regeneration.

In accordance with my invention, modulation of radio-frequency energy byvibrations of the condenser rotor plates is vprevented by providing therotor with a damping ar-l rangement, which specifically,

comprises a lea spring secured to and extendin from the rotor hub and anabsorbing mem er of felt or equivalent, pressed against the free ends ofthe rotorplates by the leaf spring.

My invention also resides in features of construction, combination, andarrangement hereinafter described and claimed;

For illustration of a structure embodying my invention, reference is tobe had to the accompanying drawings, in which:

Fig. 1 is a plan view of a multiple or gan condenser having severalrotors mounte upon a common shaft;

Fig. 2 is an elevational view section taken on line 2-2 of Fig. 1.

Referring to Figs. land 2, the stator plates S of sheet aluminum orother material are each substantially oblong or rectangular, having arecess 4 for accommodatingthe hub or sleeve 10 to which is secured aplurality of rotor plates R which are substantially equal Q theirnotches 35.

with parts inv in length and width to the stator plates. The rotorplates R may also be stamped from sheet aluminum or other suitablematerial. The axis o'f rotation of the rotor plates is oiset towards oneend of the rotor and stator plates; 1. e., as viewed in Fig. 2 theplates exgreater extent than theyv tend downwardly to do upwardly or inopposite direction.

The sheet metal housing or cradle 18 is utilized particularly when alurality of condenser units C1, C2, C3 and 4 are assembled 1n a gang,their rotor assemblies mounted upon the same shaft 19 which extendsthrough a bearing in the plate 20 secured to the end 21 of the housing18. At its other end the shaft has a conical recess engaging thecomplementary end of the bearing screw 22 held by the plate 23 securedto the other end 2A of housing 18. Each of thesleeves 10, carrylng agroup of rotor plates adapted to interleave with the stator plates ofthe correspondlng condenser, is held in suitable position on shaft 29 byset screws 25. The shaft is thrust A vilar springs 27 secured to theshield plates 28,

which are suitably fastened to the bottom 18a of the housin 18 andelectrostatically isolate the stators o? adjacent condensers, may alsobe utilized.

`The housing 18 is provided with upwardly turned side iianges 29 and endflanges 30. Secured by screws 31 to the flanges 29 are the pairs ofbrackets 32 having secured to their portions within the housing 18 thestrips 33 of insulating material to which are secured by screws 34 orequivalent the brackets 15 holding the stator plates S by engaging in Atthe right end of the shaft, Fi 1, is secured a gear segment 3 which mayrotated by any suitable means for adjusting all the condenser rotors inunison for simultaneously tuning a plurality of circuits traversed byradio frequency energy. These circuits may be utilized to couplecascaded vacuum tubes, or they may be directly coupled to each other, asin advance of a radio frequency amplifier Y or the first detector of asupkerheterodyne receiver, or one of them .may e for tuning theoscillator of a superheterodyne and the others for tuning asignal-selective system. To the member 3 may be attached a dial 36cooperating with an indicator or pointer, not shown. Secured upon thevshaft 19 is a counterweight 37 to balancethe rotor structures which maybe left at any tuning position to which adjusted without tendency tomove therefrom. Upon the iiange may be secured the upstandingstop 37aagainst which the counterweight is adapted to engage to limit the rotormovements.

In radio receiving systems in which the loud speaker is disposedadjacent the remainder of the apparatus, for example by dispositionwithin the same cabinet, there often results a continuous sound, usuallyof fixed pitch and of such intensity as to mask or materially interferewith the signal, speech or music,

sought to be recelved. Many sources of these sound disturbances havebeen isolated. I have found that particularly with condensers of thetype described, in which the rotor plates extend to substantial extentfrom the rotor shaft or hub, that the rotor plates, when set intovibration from any cause, vary the resonant frequency of'` theassociated circuits and modulate any radio frequency energy at anaudible rate. Whenthis energy is rectified as by the detector of areceiving system, the audio frequency component introduced'by thelvariations of the rotor plates appears as sound vibrations in the outputof the loud speaker. Moreover, these sound vibrations reinforce themovements of the rotor plates,

resulting in louder reproduction of the disturbance introduced by thevibration, the reaction repeating to build up the intensity of adisturbance by what may. be termed sound regeneration. This reactlontakes place even though there is no audio frequency coupling between thecircuits tuned by the condensers, as there is practically always radiofrequency ener capable of being modulated by the vibrations. Durin thereception lof signals, there is practica y always an incomingcarrier-wave, and even when a set is'not tuned to receive any signal,atmospheric disturbances supply energy vcapable of being modulated and'serve as carrier.

Kent application;,. Serial shown whlch This sound regeneration may beeliminated. by dampin the condenserrplates to` prevent them fromeinvibrated by sound from the or the condenser construction abovedescribed, and which is more articularly described and claimed .inco-pen ing No. 458,185,6.1ed

I prefer the damping'system comprises a leaf spring 38 secured at oneend, as by screws 39, to the hub 10 of the rotor assembly, with 'a pieceof felt 40 or equivalent damping niaterial interposed between -tliefreeend 41 ofthe spring. which May 31,1930,

preferably is substantially equal to the overall width of the rotorassembly and the edges of the rotor plates at or adjacent their freeends. The spring 38 is under tension firmly to press the strip 40 whichmay be suitably held thereto, as by adhesive, of the rotor plates,prohibiting any tendency of any or all of the plates to vibrate freely.In the event that the plates are temporarily set into movement by anunusually severe shock, any resulting vibrations are nevertheless sohighly damped that no continuous noise resulting appear in the output ofthe loud speaker, as the sound vibrations are not capable of maintainingthe plate vibrations.

The construction shown has the mechaniagainst the-edges l from soundregeneration will cal advantage that if the rotor plates are moved orforced beyond their position of maximum capacity, the edges of thestator plates are engaged only by the soft or yielding felt ified in anyway to accommodate attachment of the damping spring and itsappurtenances. For gang condensers I prefer to attach a separate springto each of the rotor hubs or equivalent with a separate piece of felt tobridge or overlie the edges of the rotor pates of the correspondingrotor assembly. owever, it will'be understood that other arrangementsmay fromA the spirit and substance of my invention as expressed in theappended claims.

What I claim is:

stator plates, and a damping system for preplates comventing vibrationsof said rotor prising a mass of damping material and a tensioned memberfor forcing said material be utilized without departing 1. A vari blecondenser having rotor and into engagement with the edges of saidplates. l

2. A variable condenser having 'arotor and a stator, each comprising aplurality of plates, and a damping system for preventing vibrations ofsaid rotor lates comprising a leaf spring secured to said rotor ad;acent theaxis of rotation thereof and exten ing to overlie the edges ofsaid rotor plates, and a strip of damping material firmly held by saidspring against the edges of said plates.

3. tatable' member, plates secured to said member4 and extendingtherefrom, a leaf s ring secured -to said member and extending ere- Avariable condenser comprising a rofrom in the same direction as saidplatesalidv a strip of damping material interpose tween the'free ends ofsaid` spring and said plates. l

4. A variable condenser comprisinga rotatable member, plates` secured tosaid member and projecting therefrom to one direction than in anop leafspring .secured to -sai greater extent in ositedirection, a.

member and extending therefrom in said one direction, and a strip ofdamping material interposed between the free ends of said spring andsaid plates.

5. A gang tuning condenser for radio receiving apparatus comprising arotor assembly including a rotatable shaft and a plurality of groups ofplates attached to and movable with said shaft, a plurality of leafsprings each secured to 'said assembly adjacent the axis of rotation ofsaid shaft, and overlying one of said groups of plates, and clampingmaterial pressed by each of said springs against the edges of the platesof the corresponding ou KENNETH M. MGLAUGHLN

